An elevator typically comprises an elevator car and a counterweight, which are vertically movable in a hoistway. These elevator units are interconnected to each other by a hoisting roping. The hoisting roping is normally arranged to suspend the elevator units on opposite sides of a drive wheel. For providing force for moving the suspension roping, and thereby also for the elevator units, the elevator comprises a motor for rotating the drive wheel engaging the hoisting roping. The motor is automatically controlled by an elevator control system, whereby the elevator is suitable for automatically serving passengers.
In elevators, the hoisting roping comprises at least one but typically several elevator ropes passing alongside each other. The conventional elevators have steel ropes, but some elevators have ropes that are belt-shaped, i.e. their width is substantially greater than the thickness. As with any other kind of rope, position of the belt-shaped ropes relative to the drive wheel around which it passes (in the axial direction of the drive wheel) so that none of the ropes drifts in said axial direction away from the circumferential surface area of the drive wheel against which the rope in question is intended to rest.
Typically, in prior art, position of ropes in said axial direction has been controlled by providing the drive wheel and the rope engaging the drive wheel with a ribbed or toothed shapes complementary for each other, whereby movement of the rope in said axial direction is blocked by mechanical shape-locking. One alternative way to control position of the belt-shaped ropes in said axial direction is to shape the circumferential surface areas of the drive wheel cambered (also known as crowned). Each cambered circumferential surface area has a convex shape against the peak of which the rope rests. The cambered shape tends to keep the belt-shaped rope passing around it to be positioned such that it rests against the peak thereof, thereby resisting displacement of the rope far away from the point of the peak.
A drawback of the known elevators has been that moving of a rope in the axial direction outside its intended course, and further development of the problem into even more hazardous state have not been prevented in an adequately reliable manner. This has been difficult especially with elevators where said mechanical shape-locking between the drive wheel and the rope engaging the drive wheel has been inadequately reliable or unavailable for some reason such as due to preference to utilize cambered shape of the drive wheel for rope position control.